In Motivational interviewing (Ml), change talk is theorized to 1) enhance motivation for and 2) strengthen commitment to change, thereby representing both mechanisms and a predictor of behavior change. The strength of group member change talk, i.e., ability, desire, need, reasons, and commitment either toward or away from AOD use reduction/cessation will be derived from audio recordings and transcripts from a randomized clinical trial of a 10 session adolescent AOD group treatment, using discourse analysis methods. Verbal commitment strength, (VCS) in particular, recently emerged as a predictor of and "final common pathway" to AOD use reduction. The other change talk constructs are believed to be "underlying dimensions" and uniquely and positively account for commitment variance (Amrhein, Miller, Yahne, Palmer, & Fulcher, 2003). Similar associations are hypothesized to occur within the 122, 14-17 year old participants in 21 treatment groups in this study. Positive and negative VCS trajectories across sessions are hypothesized to predict AOD use decreases and increases, respectively, at 1-, 3-, and 12-month follow- up assessments. Influences of group leader Ml skills and peer members on VCS will also be evaluated. [unreadable] [unreadable] [unreadable]